1. Field of the Invention
The present invention relates to a signal processor used for a solid-state image sensor such as a CMOS image sensor module, a data processor, and a solid-state image sensor. The signal processor is used for cellular phones with image sensors, digital cameras, and video cameras, for example.
2. Description of the Related Art
When a video signal processor for a conventional CMOS image sensor is performing analog to digital conversion or digital to analog conversion, output signals are polluted by periodic logic noise caused by a color synchronization signal and a synchronization signal issued in a horizontal blanking period. The periodic logic noise results in generation of pattern noise. The analog to digital conversion and digital to analog conversion are performed within a horizontal valid period by delaying a video signal through line memory. This prevents pollution by periodic logic noise caused by a color synchronization signal and a synchronization signal issued in a horizontal blanking period during analog to digital conversion or digital to analog conversion, so as to decrease in pattern noise (see Japanese Patent Application Laid-Open No. Hei 07-250266, for example).
However, according to the video signal processing device disclosed in Japanese Patent Application Laid-Open No. Hei 07-250266, output noise imposed on a digital video output signal at an output terminal pollutes an output signal when canceling noise in a horizontal blanking period, resulting in generation of lined random noise. Moreover, logic noise caused by digital video signal processing in a horizontal valid period may pollute signals during analog to digital conversion, and generate random noise.